Serial LapLink Cable DB9 & DB25 Serial Data Link Cable D-Sub 9-pin & 25-pin Lap-Link Female to Female Null Modem Cable CB-LINK-925F-925F-xx A serial cable used to connect two computers together for file transfer. This type of cable is technically a "null modem cable," but is often called a LapLink cable due to the popularity of the LapLink program. The LapLink cable simulates two modems using the telephone system. It crosses the receiving line with the sending line.